ARCO,CapitalVault Idaho (AP) — Two crop dusting airplanes collided near an airport in southern Idaho on Thursday and crashed to the ground, killing one of the pilots and leaving the other with life-threatening injuries, officials said.

The crash was reported at about 12:30 p.m. in an area covered by sage and grass near the airport in Arco, the Butte County Sheriff’s Office said.

Arco is about 70 miles (113 kilometers) west of Idaho Falls.

The National Transportation Safety Board and the Federal Aviation Administration were notified about the crash and the cause is under investigation, the sheriff’s office said.

The names of the pilots involved have been withheld until their families could be notified, officials said.